Polytetrafluoroethylene (PTFE), in particulate form, has been employed in preparing not only the active layer of an electrode useful in electrochemical processes, but also in the backing layer thereof. For example, particulate PTFE has been employed to impart hydrophobicity to active carbon particles employed in an active layer of an electrode. Additionally some electrode structures utilize layers of PTFE, either per se, or with pore-forming materials to form protective or backing sheets, viz., protective layers to further wetproof the active carbon black particles contained in the active layer of the electrode. The pore-forming agents are customarily utilized to impart porosity to the overall electrode structure, including in some cases, the active layer, so as to enhance contact with, for example, the oxygen or air employed in the so called "oxygen (air) cathodes". For example, in the case of oxygen (air) cathodes, the oxygen or air is flowed across the face of or bubbled through, such a cathode or cathode layer. Such oxygen (air) cathodes can be employed in chlor-alkali cells to conserve electrical energy by eliminating the formation of hydrogen at the cell cathode and thereby achieving savings estimated as high as 25% in the electrical power required to maintain such chlor-alkali cells.
Of course, when water-soluble, pore-forming agents are employed to produce such backing layers; the pore-forming agent must be removed after formation of such wetproofing (backing) layer and active layer contaiing it. Similarly some electrode structures are formed of two or even three layers, e.g., a two-layer structure wherein a backing layer is joined to an active layer which is then arranged in a cell with some form of current distributor or current collector. Three-layer laminates are composed of a backing layer which is secured to an active layer which in turn is secured to a current collector (distributor). When such structures are formed by lamination using heat and/or pressure, it is considered necessary to remove the pore-forming agent, either before, during or after the formation of the laminated assembly.
In order to retain porosity, it is preferable to remove the pore-forming agent after formation of the laminated assembly, e.g., cathode. In accordance with this invention, it was discovered that after laminating such PTFE-containing active layer, e.g. containing active carbon or carbon black, to the leachable, pore-forming/PTFE-containing hydrophobic backing layer using heat and elevated pressure, e.g., temperatures ranging from about 110.degree. to about 125.degree. C. and pressures ranging from about 4 to about 10 tons per square inch; severe blistering of the layer(s) containing the PTFE occurred when the pore-forming agent was sought to be removed during the subsequent water washing step(s), viz., the water washing operation to which such laminates were subjected after formation thereof. This blistering destroyed the usefulness of the electrodes.